If some rich entity decides to buy all (21 mill) bitcoins, what is the worth afterwards?Nothing right? A currency is worthless without circulation, so it seems to me a plausible way to attack the currency, if it should prove as disruptive as some people hope.Even before reaching that extreme, incremental buying and hoarding (or destruction) of coin would reduce the usefulness, and therefore value of bitcoin.That a bitcoin is worth as much as the cost to produce / mine it is just a proxy value - you can't use a bitcoin to get back that amount of energy / computation power - it's all backwards.

The problem would be the rich entity would have to pay A LOT to get ALL the coins. As the supply dwindled and the demand stayed "infinite", the price would exponentially increase. I know they'd have to pay me ~$10,000 a coin if I were the last person holding any besides them!

Alternatively, suppose they CAN get to a high enough % of ownership (maybe not 100%) that it kills the utility of bitcoin. All that would happen is everybody else would switch to "bitcoin2" and the value of bitcoins would plummet, destroying all the money they pumped in to accumulate those bitcoins in the first place. I'm not sure what their incentive would be to just give hundreds of millions of dollars to everybody so they can switch to a new blockchain!

Bitcoin is open-source. It doesn't take much effort for someone to launch a Shitcoin network if someone were to try shitting on the Bitcoin network in the way proposed.

If someone wants to buy all the Bitcoins - cool - I don't want a mortgage. Then they can buy all the Litecoins, then all the CosbyCoins, then all the Shitcoins, etc. They'd be playing whack-a-mole. Cat's out of the bag.

Bitcoin would still be useful even if there was only 1,000 BTC in circulation. Or 1.0 BTC, for that matter, as Bitcoin currency is divisible to eight decimal points. It might be slightly less useful if it couldn't be divided further, but it would still be useful.

If the rich entity were to then simply destroy these coins (and it was verifiable that the coins were truly destroyed) then the exchange rate would stabilize and Bitcoin could continue being used. In that scenario we'ld have to get used to referencing prices in satoshis (0.00000001 BTC) and not BTCs themselves though.

If the rich entity were to start selling the coins instead of destroying them and was to put them back into circulation there could be disruption. That could cause exchange rate volatility or price inflation even, depending on the rate they were reintroduced and the demand for them.

So yes, bitcoin is vulnerable to a rich entity hell-bent on causing grief to the currency. But doing so would take an enormous amount of money ... and spending $2 to save $1 isn't a rational economic decision.

I can't see any justification for taxpayer money being used to do this and I certainly can't see any corporation explaining to its shareholders why this was the best use of their funds either.

That a bitcoin is worth as much as the cost to produce / mine it is just a proxy value - you can't use a bitcoin to get back that amount of energy / computation power - it's all backwards.

Unlike gold mining or production of other commodities, the cost to produce a new bitcoin rises and falls -- it will equilibrate with whatever the market value is for that bitcoin (as difficulty follows price), and not the other way around. In that sense, you are correct -- Bitcoin is backwards. It does break the rules. Isn't it a novel concept!

I'm not sure it would necessarily be that expensive - at current market rate it would be $5 x 21 million , which is not a lot for a government (or even some billionaires). Granted the purchasing would have to be gradual to not spike prices, and granted it would rise a lot near the end due to scarcity. But it seems it's a cheaper attack than the "take over 51% of the network" or outcompeting the miners' computing power. And I'm not too sure how useful it would be with only 1000 BTC in circulation - if there's no liquidity, it's quite hard to have a market. And dividing it to Satoshis is only useful is the price increased by several magnitudes - and since the entity could cause a price crash at any time by dumping, that would probably not happen.I do indeed like the project, it's just that the 21 mill limit gives makes me uncomfortable, and I'm trying to see if it is (or will be) indeed a problem, or I'm just not seeing the whole picture yet.Thanks for your inputs!

I'm not sure it would necessarily be that expensive - at current market rate it would be $5 x 21 million , which is not a lot for a government (or even some billionaires). Granted the purchasing would have to be gradual to not spike prices, and granted it would rise a lot near the end due to scarcity.

Right now there aren't 21M coins in existence. Some are lost forever, and some of us wouldn't sell 100% of them at any price.